Process for separation of heavy metals and halogen from waste material or residue

ABSTRACT

A process for the separation of heavy metal and halogen from unwanted waste material or residue. Halogen is selectively extracted or washed out from the waste material. Metal is selectively extracted or washed out from the essentially halogen free waste material.

Heavy metals, such as lead and cadmium, are presented in high amounts inrest-products (coke, ashes, slag) from waste-incineration. In contactwith water the heavy metals leak into the surroundings. Heavy metalssuch as lead and cadmium are extremely toxic and poisonous, and areknown to cause human cancer and effect reproductivity. In Denmark, theamount of lead that is collected for deposition and incineration is1400-3400 tons/year (Miljøstyrelsen, 1997). After incineration around90% of the heavy metals are found in the ashes, coke and slag. Theincreased usage of PVC-material has lead to tons of waste, which isusually disposed off by incineration or deposited at controlled wastedisposal sites. Upon incineration of PVC material, ashes and coke areformed with a high content of lead and chlorine. PVC alone contribute to⅔ of the total amount of chlorine which is incinerated. In fact, thepresence of chlorine increases the leakage of heavy metals to thesurroundings. Increased amounts of waste for deposition or incinerationwill lead to an increased pollution caused by the heavy metals andchlorine.

The international patent application WO 9716230 relates to separation ofmetal chlorine compounds from metallurgical dust. The metallurgical dustis washed to remove the metal chlorine compounds, followed by extractingwith nitric acid to dissolve lead, zinc, cadmium, copper, magnesium,calcium and manganese. The pH is raised to 1.8-3.5 to precipitate iron.Finally lead, copper and cadmium is removed. The filtrate is evaporatedand decomposed to obtain solid metal oxides and calcium nitrate. Zinc isrecovered by further processing.

DE 4217133 relates to a process for removal of chlorine and heavy metalsfrom dust and slag. The process is based on washing the material with anorganic acid, filtration of the mixture and separate disposal offiltrate and filter residue. 70% of the lead is separated from the dustand slag.

In another patent application (EP 551155) heavy metals such as lead,zinc, copper and cadmium are extracted and recovered from flue dusts.This is done by treating the flue dusts with an aqueous solution ofammonium and sodium chloride. Lead is in this case dissolved as a chlorocomplex. The resulting solution is separated from the solid residue.Finally the mixture is further treated to separate zinc.

EP patent no. 482335 describes a process for removal of heavy metalsfrom fly ash particles. This is done by washing with an acidic solution,rinsing and disposing the residue. The acid washings are then treatedwith for example Ca(OH)₂ to give a heavy metal filter cake.

U.S. Pat. No. 5,102,556 proposes a process for removal of heavy metalsfrom iron. based sludges. The sludge is dissolved in hydrochloric acidand is filtered to remove lead chloride.

None of those known processes separate in a simple and economic way thewaste into pure materials and/or materials which can be disposed in thenature without problems.

These problems are solved by the present invention.

The present invention proposes a new technology for separation of heavymetals and halogens from coke, ashes, fly ash, slag, metallurgical dustand the like waste products. By exploiting the influence of pH on themetal solubility in water, metals and halogens can selectively beextracted from the waste. The separation sequence include multipleextraction and filtration stages. By treating a waste, for example cokefrom a PVC recycling process, lead can be separated from the coke into alead product of a 50-60% lead purity, which can be further concentrated.The chlorine can be separated into a salt with less than 100 ppm leadcontent. Finally, the coke product has been raffinated for more than 98%of the initial chlorine content, and 90% of the initial lead content.

The process of the invention also propose to separate heavy metals (suchas lead) by extracting in an acidic aqueous solution (nitric acid) likesome of the known processes as well as use filtration and precipitationas separation techniques. As a new feature, the process of the inventionuse changes in pH to dissolve, precipitate and separate lead andchlorine from coke.

The process of the invention is a process for separation of heavy metalsand halogen from unwanted waste material or residues containing amixture of these materials, wherein

a) the waste material is optionally comminuted,

b) carbondioxide optionally is removed from the optionally comminutedmaterial,

c) the halogen is selectively extracted or washed out from theoptionally comminuted and optionally for carbondioxide removed materialproviding an essentially halogen free waste material (A) containingheavy metal, and a liquid (B) containing the halogen,

d) the metal is selectively extracted or washed out from the wastematerial (A) from step c) at a low pH providing a waste materialessential free from heavy metal and halogen,

e) the steps c) and d) are optionally repeated, and

f) the extracted metal or metals is optionally precipitated.

The unwanted waste material can for example be a residue as produced bya PVC recycling process as described in PCT/DK96/00117 or from anincineration plant. This residue will have to be milled or in anotherway comminuted, whereas other waste materials need not be comminuted.

The heavy metal can be metals such lead, copper, zinc, cadmium,chromium, tin, manganese and nickel and mixtures of two or more metals.

The halogen can be chlorine, bromine or fluorine or a mixture of two orall three. The halogen is bound halogen, normally bound as an inorganiccompound.

Steps c) and d) can be combined into one step.

Steps c) and d) can also be repeated as b),b),b . . . c),c),c) . . . asmany times as wanted using pure water or recycled washing liquids fromformer steps, and water in the last washing step.

The process of the invention can thus be performed with or withoutrecycling of the filtrates, in order to minimise the consumption ofchemicals.

A basic pH in step c) is achieved by using a base such as Al₂OH₃, analkaline or earth alkaline metal hydroxide or a mixture thereof.Specific examples of usable bases are NaOH, CaOH₂, KOH, MgOH2. CaOH₂ ispreferred, because it leads to an end product useful as a fertiliser, asthaw salt or industrially useful in another way.

An acidic pH in step d) is achieved by using an acid. The acid can beselected from the group consisting of HCl, HNO3 and acetic acid. HCl ispreferred. By using CaOH₂ and HCl for treating the coke from a PVCrecycling process according to for example PCT/DK 9,600,117 it ispossible to convert the waste material totally in reusable materials.The lead can be separated from the coke into a lead product of a 50 to60% lead purity, which is such a high concentration, that it iseconomically feasible to recover the lead therefrom. The chlorine isseparated as CaCl₂ with a lead content of less than 100 ppm, whichpermits use of this material without polluting nature. Finally, the cokeproduct has been raffinated for more than 98% of the initial chlorinecontent and 90% of the initial lead content.

Step c) can be conducted at any pH , but pH 7-11 is preferred. Even morepreferred is pH 9-10.

Step d) can be conducted at pH 0-4, preferably pH 1-2.

In the present invention is has been shown, that the liquid-solid ratiois important. In both step c) and step d) it is possible to use a ratioof 0.5:1 to 50:1. In step c) is it preferred to use a ratio of 1.5:1 to3:1 and in step d) a ratio of 3:1 to 5:1.

It is possible to use a temperature of 0 to 200° C. in step c) as wellas in step d). Higher temperatures will often give a faster process, butat a higher cost. Step c) is therefore normally performed at roomtemperature. Step d) is usually performed at 20 to 100° C.

Extracted metal from step d) is preferably precipitated at a high pH,but it is also possible to recover the metal in another way, for exampleby electrolysis of the solution.

It is possible to use atmospheric pressure or a higher pressure.

The invention is further illustrated referring to the accompanyingcompanying drawing, where

FIG. 1 illustrates the extraction of lead as function of differentparameters.

FIG. 2 illustrates the effect of the temperature on lead solubility.

FIG. 3 is a flowsheet of a preferred process of the invention.

FIG. 4 illustrates the distribution of chlorine in products exiting theprocess.

FIG. 5 illustrates the amount of extracted chlorine from the coke.

FIG. 6 illustrates the distribution of lead exiting the process.

FIG. 7 illustrates precipitated lead in weight % of the initial amount.

FIG. 8 illustrates the purity of the lead product.

FIG. 9 illustrates the amount of lead and chlorine in the treated cokeproduct.

FIG. 10 is a flowsheet of the material balance for (experiment 501)example 1.

FIG. 11 is a flowsheet of the product distribution in (experiment 501)example 1.

FIG. 12 is a flowsheet of the material balance for (experiment 602)example 2.

FIG. 13 is a flowsheet of the product distribution in (experiment 602)example 2.

FIG. 14 is a flowsheet of the material balance for (experiment 606)example 3.

FIG. 15 is a flowsheet of the product distribution in (experiment 606)example 3.

FIG. 16 is a flowsheet of the material balance for (experiment 608)example 4.

FIG. 17 is a flowsheet of the product distribution in (experiment 608)example 4.

FIG. 18 is a flowsheet illustrating a preferred embodiment of theinvention treating PVC cable/(building) waste.

FIG. 19 is a material flowsheet for the embodiment illustrated in FIG.18.

EXPERIMENTAL PART

In the following experimental part of the specification reference ismade to removal of lead and chlorine from a coke from a PVC recyclingprocess such as for example the process of PCT/DK96/00117. The personskilled in the art will know how to modify the examples to use theinvention on other products containing other heavy metals and or otherhalogens.

The Influence of Different Parameters

In a PVC recycling process (as described in international patentapplication no. PCT/DK 96/00117), a coke product is formed, whichconsists of high amounts of chlorine (40 weight %) and approximately14190 ppm lead. The following results will illustrate how the leadsolubility is influenced by parameters such as pH, temperature,liquid-solid ratio, chlorine content and coke surface area(comminution). The influence of these parameters on the lead solubilitywill be exploited by the new technology for separation of chlorine andlead from coke and ashes.

Separation of Lead from Coke in Aqueous Suspension

In these experiments lead is separated from coke through aextraction-filtration procedure. The starting material is 50 g coke froma PVC recycling process. The coke consists of 20 g chlorine (40weight-%) and 709.5 mg lead (14190 ppm). Water is added to the cokeproduct in a liquid-solid ratio 2.6 (stage 1) and liquid-solid ratio 1.0(stage 2-11). Lead is extracted from the coke product by washing andfiltration in 11 stages. The results are illustrated in Table 1.According to Table 1, 155.93 mg of lead is removed from the coke after11 stages. This corresponds to only 22% of the initial amount of lead(709.5 mg). Approximately 94% of the lead which dissolves, is extractedafter 3 stages. The pH of the slurry to be filtered range from 5.7 to7.2. Water alone does not seem to have the extractive power for acomplete separation of lead from coke. A chlorine content of more than1% (9.753 mg/l) leads to an increase in the lead solubility.

TABLE 1 Separation of lead from chlorine rich coke product with waterLead Chlorine Volume Liquid- conc. concentration pH of Mass of Stepsolid in filtrate in filtrate of filtrate extracted no: ratio (mg/l)(mg/l) slurry (nd) lead (mg) 1 2.6 1011 85120 5.7 130 131.43 2 1.0 22125020 6.2 53 11.71 3 1.0 58 9753 6.6 55 3.19 4 1.0 37 5763 6.6 47 1.74 51.0 27 3910 6.6 57 1.54 6 1.0 22 2311 6.9 49 1.08 7 1.0 21 1212 7.1 501.05 8 1.0 21 1024 7.2 49 1.03 9 1.0 21 705 7.2 50 1.05 10  1.0 21 6717.2 50 1.05 11  1.0 20 436 7.2 53 1.06 Total 155.93

Separation of Lead from Coke at Acidic Conditions in Aqueous Suspension

The starting material is again 50 g coke, with a lead concentration of14190 ppm, and a chlorine content of 40 weight-%. Results from washingof coke product with 0.1 M nitric acid in aqueous suspension areillustrated in Table 2. According to Table 2, 563.31 mg lead isextracted after 11 stages. This corresponds to 80% of the initial amountof lead (709.5 mg). These results may be compared with Table 1, whereonly 22% of the total amount of lead was extracted after 11 stages. Thelow pH, which is created by the nitric acid, has a significant effect onthe lead solubility. Approximately 96.6% of the lead which dissolves, isextracted after 3 stages. The pH of the slurry range from 1.4 to 3.8.The solubility of lead is highest at the low pH which is created by theacidic nitric acid. Therefore, it is recommended to keep a low pH forthe extraction of lead from coke. It is interesting to note, that in thepH range 2.1-3.2 there is an increase in the lead solubility. Thiseffect is not found for the first case, with aqueous solution, where pHrange from 5.7-7.2. One explanation may be, that specific lead saltsdissolve in this pH range, leading to a more efficient separation oflead from coke.

TABLE 2 Separation of lead from chlorine rich coke- product with 0.1 Mnitric acid Lead Chlorine Liquid- conc. in conc. in pH Volume ofExtracted Stage solid filtrate filtrate of filtrate amount of lead no:ratio (mg/l) (mg/l) slurry (ml) (mg) 1 2.6 2766 108350 3.8 105 290.43 21.0 527 32995 4.1 50 26.35 3 1.0 94 11630 4.3 51 4.79 4 1.0 43 5519 4.150 2.15 5 1.0 557 2856 3.2 50 27.85 6 1.0 1322 1762 2.7 50 66.10 7 1.01160 1420 2.1 51 59.16 8 1.0 735 800 1.7 50 36.75 9 1.0 452 535 1.6 5022.60 10  1.0 271 407 1.5 50 13.55 11  1.0 271 155 1.4 50 13.55 Total563.31

The Influence of pH and Liquid-solid Ratio on Lead Solubility forChlorine Rich Coke

The influence of pH on the lead solubility is investigated for the pHrange 1-14. In addition, the effect of liquid/solid ratio (2:1 and 6:1)on the lead solubility is determined. Further, the effect of thepresence of chlorine on the lead solubility is analysed. From Table 3,it can be noted, that a high solubility of lead can be obtained both atbasic and acidic conditions. Around 40% of the lead content can bedissolved in 1 stage at pH 2, or 33% at pH 12.

There is a minimum in lead solubility in a pH interval around pH 9-10.The variation in lead solubility with pH can be exploited for theseparation of chlorine and lead from coke/ashes/slag.

TABLE 3A Lead solubiiity as function of pH for chlorine- rich coke (L:S= 2) Removed lead in Lead conc. weight- %, 1 pH (mg/l) stage (L:S = 2)0.5 1426 0.20 1.1 1983 0.28 2.1 2770 0.39 3.1 1210 0.17 4.2 1879 0.265.1 1854 0.26 6.1 1234 0.17 6.1 1167 0.16 7.1 188 0.03 7.9 36 0.01 8.914 0.00 9.9 41 0.01 11.0 2285 0.32 11.9 2362 0.33

TABLE 3B Lead Solubility as function of pH for chlorine- rich coke (L:S= 6) Removed lead in Lead conc. weight- %, 1 pH (mg/l) stage (L:S = 2)0.0 1572 0.66 0.5 1236 0.52 1.1 1416 0.60 2.2 1077 0.46 3.2 860 0.36 4.2807 0.34 5.1 570 0.24 6.1 332 0.14 6.3 307 0.13 7.4 81 0.03 8.3 10 0.009.4 7 0.00 10.0 4 0.00 11.0 29 0.01 12.0 554 0.23 13.0 44 0.02 14.0 2690.11

From Table 3B, it can be noted that lead can be dissolved both at acidicand at basic conditions. Again, a minimum in lead solubility existaround pH 9-10. Around 60% of the lead content can be dissolved in 1stage at pH around 2, or 23% at pH around 12. The lead solubility is atbasic conditions only ⅓ of the lead solubility at acidic conditions.

It can be noted, that the liquid-solid ratio has a big impact on thelead solubility. If the liquid-solid ratio is increased from 2:1 to 6:1at pH 1.1, the amount of lead removed increases from 28% to 60%. Byexploiting the differences in pH and liquid-solid ratio on the leadsolubility, a lead and chlorine free coke product can be obtained.

The Influence of pH and Liquid-solid Ratio on Lead Solubility forChlorine Free Coke

In the following experiments, the influence of pH and liquid-solid ratioon the lead solubility has been investigated for chlorine-free coke. Theinvestigated pH range is 1-14 and the liquid-solid ratios investigatedare 6:1 and 2:1. Table 5 illustrates that lead may be dissolved both atacidic and at basic conditions. A wide pH interval exists, in which thelead solubility is at a minimum (pH 7-11). Around 40% of the leadcontent can be dissolved in 1 stage at pH 0, or 15 % at pH 14.

TABLE 4 Lead solubility as function of pH for chlorine- free coke (L:S =2) Removed lead in Lead conc. weight- %, 1 step pH (mg/l) (L:S = 2) 0.06790 0.39 1.0 4621 0.26 2.1 2738 0.16 3.1 94 0.01 4.1 57 0.00 5.0 260.00 5.9 28 0.00 6.9 14 0.00 7.1 65 0.00 8.1 19 0.00 9.0 12 0.00 10.0 100.00 11.5 41 0.00 12.2 131 0.01 14.0 2651 0.15

TABLE 5 Lead solubility as function of pH for chlorine free coke (L: S =6) Removed lead Lead conc. in weight %, pH (mg/l) 1 step, L: S = 6 0.03519 0.60 1.0 2696 0.46 2.1 1772 0.30 3.1 240 0.04 4.0 75 0.01 5.1 320.01 6.0 27 0.00 7.0 39 0.01 7.2 8 0.00 8.3 5 0.00 9.0 4 0.00 10.2 30.00 11.0 3 0.00 12.0 6 0.00 13.0 96 0.02 14.0 1174 0.20

From Table 5 it can again be noted, that lead is soluble both at acidicand at basic conditions. The lead solubility at basic conditions is ⅓ ofthe lead solubility at acidic conditions. The wide pH interval whichsignifies the minimum in lead solubility range, from pH 7 to pH 12.Approximately 60% of the lead content can be dissolved in 1 stage aroundpH 0, or 20% around pH 14. Increasing the liquid-solid ratio by a factor3, leads to an increase in the dissolved amount of lead from 16 weight %(2:1) to 30 weight % (6:1).

In FIG. 1 the amount of extracted lead, is illustrated as function ofpH, liquid-solid ratio and type of coke (chlorine rich/chlorine freecoke). It can be noted, that the amount of extracted lead is highest ata low pH (0-2), approaches a minimum, and increases again at pH 10-12.The lead content can therefore be dissolved at both acidic and basicconditions, but the most efficient extraction is obtained at acidicconditions. Compared with the chlorine free coke, the amount ofextracted lead is higher for chlorine rich coke. For chlorine-free cokethe amount of extracted lead is at a minimum in a wide pH range (pH4-12). For chlorine rich coke, the amount of extracted lead is at aminimum in a smaller pH range (pH 8-10). By exploiting the differencesin pH and liquid-solid ratio on the lead extraction, a lead and chlorinefree coke product can be obtained.

Based on the experimental data one can easily see the differences in theamount of extracted lead with pH and choose the optimal parameters forthe process of the invention. This can be exploited to selectivelyseparate both lead and chlorine from coke.

Similar experiments can be performed to determine the optimal parametersfor other heavy metals and/or other halogens.

The Influence of Temperature on Lead Solubility

The effect of temperature on the lead solubility has been investigatedfor 20, 50 and 80° C., and is illustrated in FIG. 2. An increase intemperature from 20° C. to 80° C. leads to a 15 % increase in the amountof extracted lead.

GENERAL METHOD DESCRIPTION

On the drawing one example of a possible flowsheet for the separation ofchlorine and lead from coke is illustrated in FIG. 3. The flowsheetconsists of a mill for comminution of coke, a suspension tank for mixingcoke with aqueous solutions (acidic or basic), a slurry pump andfiltration equipment. The suspension tank includes equipment forstirring and measurements of pH and temperature. In FIG. 3, steps of theextraction-filtration procedure is illustrated. In order to re-use asmuch of the chemicals (sodium hydroxide, nitric acid) and water aspossible, wash water is recycled within the chlorine and leadseparations. It should be noted that parameters such as liquid-solidratio, temperature, comminution time, pH, type of acid/base and chlorinecontent in coke affect the lead recovery.

Step 1: Comminution

Chlorine- and lead rich coke (or ashes, slag) is comminuted to asuitable size in 5-10 minutes. This is done to decrease the particlesize of the coke, which leads to an efficient extraction of the chlorineand lead from the coke.

Step 2: Separation of Chlorine From Coke

Water is added to the coke, resulting in a suitable liquid-solid ratio.To optional removal of carbon dioxide from the solution, pH is set to<4, using nitric acid or hydrochloric acid . Thereafter, pH is raised to9.5 with 6M sodium hydroxide during stirring for 30 minutes. At this pHthe lead is insoluble. The chlorine can be removed from the coke byfiltration in 3 stages.

Step 3: Separation of Lead From Coke

The chlorine free, lead rich coke is charged to a suspension of water ina suitable liquid-solid ratio. pH is lowered to around 1.0 duringstirring for 30 minutes with 0.1 M nitric acid. At this pH, lead isdissolved into the aqueous suspension. Lead can be separated from thecoke using filtration in 3 stages.

Step 4: Purification of Lead

To the filtrate from step 3 base is added (sodium hydroxide), and pH israised to approximately 9.5. The lead in the filtrate precipitates assolid lead oxide. The lead oxide is filtered off from the solution.Finally, the lead product may be dried in an oven.

Step 5: Purification of Chlorine Rich Salt

The chlorine rich solution is concentrated by drying. A chlorine richsalt is formed, which in this example is CaCl₂.

Step 6: Purification of Coke

In steps 1-3, the coke is converted to a fine particle product, that hasbeen purified from lead and chlorine. The chlorine and lead-free cokemay finally be dried to remove excess moisture.

Equipment

Slurry pump, suspension tank, filtration equipment, stirrer, mill, pHmeasurer, temperature measurer.

DETAILED METHOD DESCRIPTION

The first time the separation of lead and chlorine takes place, purewater is employed in all chlorine and lead filtration steps (see Table7). The filtrates are collected and filtrates from the second and thirdfiltration are recycled to be re-used in future filtration steps (setable 8). The steps described in the following are based on that thewater from the previous separation is reused.

Separation of Lead and Chlorine from Coke with Recycling of ProcessWater

Step 1: Comminution

Chlorine- and lead rich coke (or ashes, slag) is disintegrated to asuitable size in 5-10 minutes.

Step 2: Separation of Chlorine from Coke

Chlorine Filtration 1

Water is taken from chlorine filtration no.2 (1 a), and is added to themill. Chlorine and lead rich coke is mixed with the water to a suitableliquid-solid ratio (minimum 2:1), and is blended for 10 minutes. Themixture is added to the suspension tank, and the pH is adjusted to 3-4,to remove CO₂ gas from the system. This CO₂ removal may optionally beperformed at any of the chlorine filtration stages. The pH is thenraised to 9.5 with sodium hydroxide. The mixture is stirred for 30minutes. The suspension is filtered. The filtrate (1 b) is removed fromthe system as CaCl₂ suspension product, and the coke (1 c) obtainedafter filtration is recycled to the suspension tank.

Chlorine Filtration 2

In the second chlorine filtration, water from the third chlorinefiltration (2 a) is added to the suspension tank with the coke (1 c) ina suitable liquid-solid ratio. pH is adjusted to 9.5, and the mixture isstirred for 30 minutes. The solution is filtered, and the filtrate (2 b)is recycled to the chlorine filtration no. 1. The coke (2 c) is afterfiltration recycled to the suspension tank.

Chlorine Filtration 3

In the third chlorine filtration, pure water (3 a) is added to thesuspension tank together with the coke (2 c) in a suitable liquid-solidratio. pH is adjusted to 9.5, and the mixture is stirred for 30 minutes.The solution is filtered, and the filtrate (3 b) is recycled to thechlorine filtration no. 2. The chlorine lean coke (3 c) is recycled tothe suspension tank for further purification from lead.

Step 3: Separation of Lead from Coke

Lead Filtration 1

Water is taken from lead filtration no. 2 (4 a). The water is mixed withthe coke (3 c) in the suspension tank in a suitable liquid-solid ratio.pH is adjusted to 1.0 with nitric acid to dissolve lead. The mixture isstirred for 30 minutes at a suitable temperature. The solution isfiltered. The filtrate is the lead product (4 b) which is removed fromthe system. The coke (4 c) is recycled to the suspension tank.

Lead Filtration 2

Water is taken from lead filtration no. 3 (5 a) and is mixed with thecoke (4 c) in the suspension tank in a suitable liquid-solid ratio. pHis adjusted to 1.0, and the mixture is stirred for 30 minutes at asuitable temperature. The solution is filtered, and the filtrate (5 b)is recycled to the lead filtration no. 1. The coke (5 c) is recycled tothe suspension tank.

Lead Filtration 3

Pure water (6 a) is added to the suspension tank, and is mixed with thecoke (5 c) in a suitable liquid-solid ratio. pH is adjusted to 1.0, andthe mixture is stirred for 30 minutes at a suitable temperature. Thesolution is filtered, and the filtrate (6 b) is recycled to the leadfiltration no.2. The coke product (6 c) is now separated from lead andchlorine.

TABLE 7 Initial steps in separation scheme Step In Filtrate CokeChlorine filtration 1 1a 1b 1c Pure water CaCl₂ product RecycledChlorine filtration 2 1a 2b 2c Pure water to Cl. filtration 1 RecycledChlorine filtration 3 3a 3b 3c Pure water to Cl. filtration 2 RecycledLead filtration 1 4a 4b 4c Pure water Lead product Recycled Leadfiltration 2 5a 5b 5c Pure water to lead filtration 1 Recycled Leadfiltration 3 6a 6b 6c Pure water to lead filtration 2 Coke product

TABLE 8 Steps in counter current separation scheme Step In Filtrate CokeChlorine filtration 1 1a 1b 1c Water from Cl CaCl₂ product Recycledfiltr.2 Chlorine filtration 2 2a 2b 2c Water front Cl to Cl. filtration1 Recycled filtr.3 Chlorine filtration 3 3a 3b 3c Pure water to Cl.filtration 2 Recycled Lead filtration 1 4a 4b 4c Water from Pb Leadproduct Recycled filtr.2 Lead filtration 2 5a 5b 5c Water from Pb tolead filtration 1 Recycled filtr.3 Lead filtration 3 6a 6b 6c Pure waterto lead filtration 2 Coke product

Steps 4-6 are performed as described in the foregoing

Sequential Separation of Lead and Chlorine from Coke without Recyclingof Process Water

If desired, the wash-water needs not to be recycled within the chlorineand lead separation steps. Therefore, pure water can be used in everystep. This will increase the use of chemicals, water and waste streams.The separation will occur according to Table 7, but with no recycling offiltrates between the filtration steps.

General Results From Applying the Method of the Invention

Results

1) A lead concentrate with 50-60 weight % lead content, which canfurther raffinated

2) A chlorine product (salt) with less than 100 ppm lead.

3) Coke with less than 0.4 weight % lead, 0.5 weight % chlorine

Results From Separation of Chlorine From Coke

FIG. 4 illustrates that 1-2 weight % of the initial chlorine amount inthe coke is lost in the lead product, and a very small fraction is lostin the coke (less than 0.5 weight % of the initial chlorine amount).

FIG. 5 illustrates that more than 98 weight % of chlorine is extractedfrom the coke into the CaCl₂ product.

Results From Separation of Lead From coke

Only 5-8 weight % of the total amount of lead which exit the process isallocated to the coke (see FIG. 6). This corresponds to only 0.4 weight% lead in the coke. A very small fraction of the lead is lost in thelead filtrate and in the CaCl₂ product. 95-98 weight % of the lead whichexits the process is allocated to the lead product.

In FIG. 7, the amount of precipitated lead is illustrated as weight % ofthe initial amount in the coke. Approximately 95% of the initial amountof lead in coke is precipitated into a lead product. This indicates ahigh recovery of lead.

The purity of the lead product is, according to FIG. 8, 50-60%.

The concentrations of lead and chlorine in the coke product areillustrated in FIG. 9. The coke consists of approximately 0.4 weight %lead and 0.5 weight % chlorine.

EXAMPLES 1-4

The process can also be performed by downstream processing, wherecalcium chlorine and lead are removed from the coke in anextraction-filtration procedure (see FIG. 10-17). The extraction andfiltration is repeated in several steps to ensure that as much chlorineand lead as possible is removed from the coke. Important parameters inthe downstream filtration procedure are: extraction temperature,liquid-solid ratio, pH and comminution time. The values of theseparameters in the examples 1-4 (experiments 501, 602, 606 and 608) areillustrated in Table 9.

TABLE 9 Parameter variation for extraction of lead and chlorine fromcoke in example 1-4 Example no. Comminution Temperature (Experiment no.)(min) (° C.) Liquid/solid ratio pH Ex. 1 (Exp. 501) 10 Cl 20 6:1 9.5 Pb50 6:1 1.0 Ex. 2 (Exp. 602) 10 Cl 20 6:1 9.5 Pb 20 6:1 1.0 Ex. 3 (Exp.606) 10 Cl 20 2:1 9.5 Pb 20 2:1 1.0 Ex. 4 (Exp. 608) 10 Cl 30 2:1 9.5 Pb20 4:1 1.0

The material balances and product distribution for each experiment areillustrated in FIGS. 10-16. Experiment 501 and 602 have been performedwith an extraction-filtration procedure which employs de-ionised waterin all steps. In experiment 606 and 608 recycling of aqueous filtratebetween the steps have been employed. Therefore these experiments aredescribed separately. A detailed illustration of the recycling processof experiment 606 and 608 is given in FIG. 17.

Example 1 (Experiment 501) Example 2 (Experiment 602)

Separation of Lead and Chlorine from Coke without Recycling of ProcessWater (see FIGS. 10-13)

Step 1: Comminution and Formation of a Coke Suspension

The coke from the reactor is mixed with de-ionised water (400 ml) in amill for 10 minutes.

Step 2: Separation of Chlorine from Coke

The liquid/solid ratio is set to 6:1 using de-ionised water. Theextraction of chlorine begins, at 20° C., with a raise in pH to 9.5,using sodium hydroxide. The solution is stirred for 30 minutes. Around apH of 9.5 the solubility of lead in the solution is at a minimum.Therefore the chlorine can be removed selectively from the coke byfiltration. The filtrate is an aqueous suspension of calcium chlorine.

Step 3: Separation of Lead from Coke

The chlorine-free coke is mixed with water to a liquid-solid ratio of6:1. The pH is lowered to 1.0 using nitric acid to dissolve as much leadas possible into the solution. The temperature is set to 50° C. (20° C.in experiment 602). Again, the mixture is stirred for 30 minutes. Themixture is filtered in all 2 times. The filtrate from the first leadextraction is the lead rich product which is sent to further processing.

Step 4: Purification of Lead

To the lead rich filtrate from step 3 sodium hydroxide is added to pH9.5 (at 20° C.), in order to precipitate lead. The precipitated lead isfiltered and the filter cake is the lead product.

Step 5: Purification of Chlorine Rich Salt

The chlorine rich solution is concentrated by drying, and the saltcalcium chloride is formed.

Step 6: Purification of Coke

The coke is after filtration dried and represents the chlorine and leadfree coke.

Example 3 (Experiment 606) Example 4 (Experiment 608)

Separation of Lead and Chlorine from Coke with Recycling of ProcessWater (see FIGS. 14-17)

The chlorine and lead is separated sequentially from the coke, andaqueous filtrates are recycled (see FIGS. 14-17) within the process toreduce the consumption of water, nitric acid and sodium hydroxide byperforming a counter current extraction process. The downstreamseparation procedure is performed as in a multi-stageextraction-filtration procedure (see Table 10).

TABLE 10 Steps in separation scheme Step In Filtrate Coke Chlorine 1a 1b1c filtration 1 Water from Cl filtr.2 CaCl₂ product Recycled Chlorine 2a2b 2c filtration 2 Water from Cl filtr.3 to Cl. filtration 1 RecycledChlorine 3a 3b 3c filtration 3 Pure water to Cl. filtration 2 RecycledLead 4a 4b 4c filtration 1 Water from Pb filtr.2 Lead product RecycledLead 5a 5b 5c filtration 2 Water from Pb filtr.3 to lead filtration 1Recycled Lead 6a 6b 6c filtration 3 Pure water to lead filtration 2 Cokeproduct

The first time the separation of lead and chlorine takes place, purewater is employed in all chlorine and lead filtration steps. Thefiltrates are collected and filtrates from the second and thirdfiltration are recycled to be re-used in future filtration steps. Thesteps described in the following (and in Table 10) are based on that thewater from the previous separations is used in a counter currentextraction mode. Optionally the pH is lowered with an acid to removeexcess carbonate from the solution in the form of carbondioxide gas.

Step 1: Comminution and Formation of a Coke Suspension

The coke from the reactor is mixed in a mill with water for 10 minutes.

Step 2: Separation of Excess Carbonate

The pH is lowered with an acid to 3.0 to remove excess carbonate fromthe solution in the form of carbon dioxide gas from the suspension. Thisstep may optionally be performed after any of the chlorine filtrationstages.

Step 3: Separation of Chlorine from Coke

Chlorine Filtration 1

Recycled water (1 a), see Table 1, is mixed with coke to a suitableliquid-solid ratio (2:1) at a suitable temperature (20° C. or 30° C.) .The pH is raised to 9.5 with sodium hydroxide. The mixture is stirredfor 30 minutes. The suspension is filtered. The filtrate (1 b) isremoved from the system as calcium chloride product, and the coke (1 c)obtained after filtration is recycled to the suspension tank.

Chlorine Filtration 2

In the second chlorine filtration, water (2 a) is added to thesuspension tank with the coke (1 c) in a suitable liquid-solid ratio. pHis adjusted to 9.5, and the mixture is stirred for 30 minutes. Thesolution is filtered, and the filtrate (2 b) is recycled to the chlorinefiltration no. 1 (1 a=2 b). The coke (2 c) is after filtration recycledto the suspension tank.

Chlorine Filtration 3

In the third chlorine filtration, pure water (3 a) is added to thesuspension tank together with the coke (2 c) in a suitable liquid-solidratio. pH is adjusted to 9.5, and the mixture is stirred for 30 minutes.The solution is filtered, and the filtrate (3 b) is recycled to thechlorine filtration no. 2 (2 a= 3 b). The chlorine lean coke (3 c) isrecycled to the suspension tank for lead separation.

Step 4: Separation of Lead from Coke

Lead Filtration 1

Water (4 a) is mixed with the coke (3 c) in the suspension tank in asuitable liquid-solid ratio (2:1 or 4:1). The temperature was set to 20°C. pH is adjusted to 1.0 with nitric acid to dissolve lead. The mixtureis stirred for 30 minutes at a suitable temperature. The suspension isfiltered. The filtrate is the lead product (4 b) which is removed fromthe system. The coke (4 c) is recycled to the suspension tank.

Lead Filtration 2

Water (5 a) is mixed with the coke (4 c) in the suspension tank in asuitable liquid-solid ratio. pH is adjusted to 1.0 with an acid, and themixture is stirred for 30 minute at a suitable temperature. Thesuspension is filtered, and the filtrate (5b) is recycled to the leadfiltration no. 1 (4 a= 5 b). The coke (5 c) is recycled to thesuspension tank.

Lead Filtration 3

Pure water (6 a) is added to the suspension tank, and is mixed with thecoke (5 c) in a suitable liquid-solid ratio. pH is adjusted to 1.0 withan acid, and the mixture is stirred for 30 minutes at a suitabletemperature. The suspension is filtered, and the filtrate (6 b) isrecycled to the lead filtration no.2 (5 a= 6 b). The coke product (6 c)is now separated from lead and chlorine.

Step 5: Purification of Lead

See description of step 4 described in examples 1 and 2 above.

Step 6: Purification of Coke and Calcium Chloride Products

See description of step 5 and 6 described in examples 1 and 2 above.

The three main products are: 1) lead and chlorine free coke, 2) calciumchloride and 3) lead product.

Data for the described examples in terms of amount of coke in feedstream and product distribution (weight % of product of amount coke infeed) are given in Table 11.

TABLE 11 Amount coke in feed stream and product distri- bution Exampleno. CaCl₂ product Ph-product coke Experiment no.) coke (g) (weight %)(weight %) (weight %) Ex. 1 (Exp. 501) 326.6 57.7 3.9 38.4 Ex. 2 (Exp.602) 329.6 58.7 3.6 37.7 Ex. 3 (Exp. 606) 1966.0 55.0 3.0 42.0 Ex. 4(Exp. 608) 5883.0 57.5 3.8 38.7

According to the invention a methodology has thus been developed forextraction of heavy metals and halogens, especially lead and chlorinefrom chlorine rich waste products such as:

Chlorine and lead rich coke from a PVC recycling process

Chlorine and lead rich residues or ashes/slag from incineration

The present invention has described a new technology for the separationof heavy metals and halogens, such as lead and chlorine from coke, ashesand/or slag. The new technology exploits differences in lead solubilitywith pH to separate lead and chlorine from coke. This work hasillustrated that comminution, pH, temperature, liquid-solid ratio andcomminution has a significant effect on the lead solubility in aqueoussuspensions. The coke product has a lead content lower than 0.4 weight %and a chlorine content lower than 0.5 weight %.

What is claimed is:
 1. A process for separation of a heavy metal andhalogen from a waste material containing a mixture of the heavy metaland halogen, said waste material being selected from the groupconsisting of a waste product obtained from incineration of PVC materialand a residue obtained from a decomposition of PVC material, saidprocess comprising the steps of: (i) selectively extracting the halogenfrom the waste material at a pH value between 7 and 11 to obtain anextracted waste material containing the heavy metal and a liquidcontaining the halogen; (ii) selectively extracting the heavy metal fromthe extracted waste material at a pH value between 0 and 4 to obtain acleaned waste material; and (iii) optionally precipitating metalextracted in step (ii).
 2. The process according to claim 1, wherein theselective extraction of the halogen from the waste material in step (i)comprises a plurality of halogen extraction stages.
 3. The processaccording to claim 2, wherein a sufficient number of said extractionstages are conducted for the process to effect an extraction of morethan 98% of an initial halogen content of the waste material.
 4. Theprocess according to claim 1, wherein the selective extraction of theheavy metal from the waste material in step (ii) comprises a pluralityof heavy metal extraction stages.
 5. The process according to claim 4,wherein a sufficient number of the heavy metal extraction stages areconducted for the process to effect an extraction of more than 90% of aninitial heavy metal content of the waste material.
 6. The processaccording to claim 1, wherein the waste material is comminuted prior tothe selective extraction of step (i).
 7. The process according to claim1, comprising removing carbon dioxide from the waste material prior tothe selective extraction of step (i).
 8. The process according to claim1, wherein the selective extraction of step (i) comprises adjusting thepH value of an extraction medium with a base selected from the groupconsisting of an alkali metal hydroxide, an alkaline earth metalhydroxide and a mixture thereof.
 9. The process according to claim 8,wherein the base is NaOH or CaOH.
 10. The process according to claim 1,wherein the selective extraction of step (ii) comprises adjusting the pHvalue of an extraction medium with an acid selected from the groupconsisting of HCl, HNO₃ and acetic acid.
 11. The process according toclaim 10, wherein the acid is HCl or HNO₃.
 12. The process according toclaim 1, wherein the heavy metal is selected from the group consistingof lead, copper, zinc, cadmium, chromium, tin, manganese, nickel andmixtures thereof.
 13. The process according to claim 1, wherein thehalogen is selected from the group consisting of chlorine, fluorine, andbromine.
 14. The process according to claim 1, wherein the selectiveextraction of step (i) is conducted at a pH value between 9 and
 10. 15.The process according to claim 13, wherein the selective extraction ofstep (ii) is conducted at a pH value between 1 and
 2. 16. The processaccording to claim 1, wherein the ratio of liquid to solid of theextracted waste material of step (i) is 1.5:1 to 50:1.
 17. The processaccording to claim 16, wherein a ratio of liquid to solid or theextracted waste material of step (i) is 1.5:1 to 3:1.
 18. The processaccording to claim 1, wherein the ratio of liquid to solid of thecleaned waste material of step (ii) is 0.5:1 to 50:1.
 19. The processaccording to claim 18, wherein a ratio of liquid to solid of the cleanedwaste material is 3:1 to 5:1.
 20. The process according to claim 1,wherein the selective extraction of step (i) is performed at atemperature of 0° to 200° C.
 21. The process according to claim 1,wherein the selective extraction of step (ii) is performed at atemperature of 20° C. to 100° C.
 22. A process according to claim 1,wherein the extracted metal of metals from step ii) are precipitated ata pH valve about 9.5.
 23. The process according to claim 1, wherein thehalogen is selectively extracted to obtain an essentially halogen freewaste material containing heavy metal, and a liquid containing halogen.24. The process according to claim 1, wherein the heavy metal isselectively extracted to obtain a cleaned waste material essentiallyfree from heavy metal and halogen.